Heaven's Plateau
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Heaven's Plateau clear sky chart from 2005-11-06 to 2024-02-25.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	10% 5% 2 3 3 2 3 3 4 5% 61%	78535
	Night	12% 5% 2 3 3 2 3 3 4 5% 58%	80789
Transparency	Day	26% 4 8% 19% 24% 20%	78248
	Night	29% 4 8% 19% 22% 18%	80597
Seeing	Day	12% 12% 30% 30% 12% 4	14176
	Night	13% 4 15% 36% 26% 6%	23690

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	21% 10% 2 3 3 2 2 3 3 5% 45%	2539
	11th to 20th	Day	21% 8% 3 6% 5% 3 4 4 4 5% 37%	2736
	21st to end	Day	22% 10% 2 5% 4 3 4 3 5% 6% 36%	3146
February	1st to 10th	Day	20% 8% 2 3 3 2 3 3 4 5% 47%	1710
	11th to 20th	Day	14% 10% 3 4 3 2 3 4 3 7% 47%	1840
	21st to end	Day	20% 11% 3 3 4 2 3 3 4 4 44%	1521
March	1st to 10th	Day	19% 11% 3 6% 4 3 5% 4 5% 5% 36%	1809
	11th to 20th	Day	20% 9% 2 4 4 3 4 4 4 6% 40%	1980
	21st to end	Day	18% 8% 3 4 5% 3 4 3 4 7% 42%	2291
April	1st to 10th	Day	16% 7% 2 4 4 2 4 4 4 7% 47%	2160
	11th to 20th	Day	13% 5% 2 4 3 2 2 3 5% 5% 54%	2129
	21st to end	Day	12% 3 2 3 3 2 2 3 4 6% 60%	2160
May	1st to 10th	Day	9% 5% 1 3 2 1 2 4 5% 5% 61%	2200
	11th to 20th	Day	7% 4 2 2 3 2 4 3 3 6% 64%	2436
	21st to end	Day	10% 4 1 3 3 2 3 3 5% 6% 59%	2723
June	1st to 10th	Day	6% 3 1 4 3 2 3 3 4 7% 66%	2520
	11th to 20th	Day	2 1 1 2 2 1 2 2 3 4 80%	2520
	21st to end	Day	2 2 1 2 1 1 2 2 2 3 82%	2520
July	1st to 10th	Day	1 1 1 1 1 1 2 2 3 87%	2520
	11th to 20th	Day	2 1 1 2 1 1 2 2 3 3 84%	2520
	21st to end	Day	1 1 1 2 2 1 2 2 3 4 81%	2593
August	1st to 10th	Day	2 1 1 2 2 1 2 2 3 4 82%	2311
	11th to 20th	Day	1 1 1 1 1 2 2 3 4 84%	2122
	21st to end	Day	1 1 2 1 1 2 2 2 87%	2376
September	1st to 10th	Day	3 1 1 1 2 1 2 3 87%	2160
	11th to 20th	Day	2 2 1 2 2 1 2 3 3 4 77%	2152
	21st to end	Day	4 2 1 1 2 1 2 2 3 4 78%	1976
October	1st to 10th	Day	6% 2 2 2 2 2 2 3 4 6% 70%	1800
	11th to 20th	Day	6% 2 1 2 2 2 3 4 4 6% 69%	1800
	21st to end	Day	8% 2 1 3 3 2 2 4 4 4 67%	1980
November	1st to 10th	Day	12% 5% 2 3 4 2 3 4 4 7% 53%	1680
	11th to 20th	Day	11% 3 1 3 3 2 4 3 4 7% 57%	1710
	21st to end	Day	12% 6% 1 3 4 2 2 4 4 7% 55%	1653
December	1st to 10th	Day	16% 6% 2 4 3 2 4 3 4 6% 52%	1520
	11th to 20th	Day	28% 8% 2 5% 4 2 4 3 4 5% 34%	1928
	21st to end	Day	14% 8% 3 5% 5% 3 5% 5% 6% 8% 39%	2794
January	1st to 10th	Night	16% 9% 2 4 4 2 3 3 5% 6% 46%	4406
	11th to 20th	Night	23% 8% 2 5% 5% 3 4 5% 5% 5% 36%	4228
	21st to end	Night	22% 9% 2 5% 5% 3 4 4 4 6% 35%	4521
February	1st to 10th	Night	18% 7% 2 4 4 2 2 3 4 6% 49%	2470
	11th to 20th	Night	16% 8% 2 4 3 2 3 4 5% 7% 47%	2227
	21st to end	Night	18% 9% 2 3 2 2 3 3 4 5% 50%	1829
March	1st to 10th	Night	21% 11% 2 3 3 2 3 4 3 5% 42%	2147
	11th to 20th	Night	19% 7% 2 4 4 2 4 4 5% 7% 43%	1980
	21st to end	Night	19% 7% 2 3 4 2 4 3 4 6% 46%	2063
April	1st to 10th	Night	15% 6% 1 4 4 2 4 4 4 6% 49%	1800
	11th to 20th	Night	13% 5% 2 3 3 2 4 3 4 6% 55%	1779
	21st to end	Night	10% 4 1 3 3 2 3 3 5% 7% 59%	1800
May	1st to 10th	Night	9% 4 1 2 2 2 2 4 5% 6% 63%	1757
	11th to 20th	Night	7% 2 2 2 2 1 2 4 5% 8% 66%	1452
	21st to end	Night	7% 4 1 3 3 2 2 3 4 7% 65%	1552
June	1st to 10th	Night	5% 3 1 2 3 1 2 4 4 6% 69%	1440
	11th to 20th	Night	1 1 1 1 1 2 2 4 4 82%	1440
	21st to end	Night	2 1 1 2 2 1 1 1 2 3 84%	1440
July	1st to 10th	Night	1 1 1 1 1 1 2 3 89%	1440
	11th to 20th	Night	2 2 1 2 1 1 2 2 2 3 83%	1440
	21st to end	Night	3 2 1 2 2 2 3 3 2 4 77%	1721
August	1st to 10th	Night	3 2 1 2 1 1 2 2 3 3 79%	1626
	11th to 20th	Night	1 1 1 1 2 1 2 3 5% 4 79%	1780
	21st to end	Night	2 1 2 1 1 1 1 2 3 87%	1980
September	1st to 10th	Night	2 1 1 1 1 2 3 88%	1800
	11th to 20th	Night	4 2 1 1 1 2 2 2 3 81%	1806
	21st to end	Night	3 2 1 1 1 2 2 2 2 4 81%	1980
October	1st to 10th	Night	5% 2 1 2 3 2 2 3 3 4 72%	2160
	11th to 20th	Night	6% 2 1 1 2 1 3 3 3 5% 72%	2160
	21st to end	Night	7% 1 1 2 2 2 2 2 3 5% 72%	2376
November	1st to 10th	Night	13% 5% 1 2 3 2 3 3 4 6% 59%	2397
	11th to 20th	Night	11% 3 2 3 4 2 3 4 4 7% 58%	2470
	21st to end	Night	13% 4 2 4 3 2 3 3 3 6% 57%	2524
December	1st to 10th	Night	18% 6% 1 4 3 2 3 3 4 6% 51%	2660
	11th to 20th	Night	29% 7% 2 4 3 2 3 4 5% 6% 35%	3276
	21st to end	Night	17% 8% 3 5% 6% 4 4 5% 5% 7% 36%	4862

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	44% 4 8% 24% 17% 4	2539
	11th to 20th	Day	50% 6% 9% 13% 13% 9%	2736
	21st to end	Day	49% 6% 9% 19% 12% 5%	3146
February	1st to 10th	Day	41% 3 7% 21% 17% 10%	1710
	11th to 20th	Day	38% 4 8% 20% 24% 6%	1850
	21st to end	Day	45% 3 7% 22% 19% 5%	1521
March	1st to 10th	Day	49% 4 11% 16% 16% 4	1809
	11th to 20th	Day	44% 5% 8% 23% 16% 4	1980
	21st to end	Day	42% 7% 15% 21% 12% 4	2291
April	1st to 10th	Day	37% 5% 13% 22% 17% 6%	2160
	11th to 20th	Day	32% 4 13% 27% 19% 6%	2132
	21st to end	Day	26% 4 13% 30% 23% 4	2160
May	1st to 10th	Day	23% 4 13% 27% 26% 7%	2200
	11th to 20th	Day	23% 3 10% 27% 29% 7%	2439
	21st to end	Day	26% 4 14% 28% 22% 6%	2724
June	1st to 10th	Day	20% 4 10% 24% 29% 13%	2520
	11th to 20th	Day	10% 2 6% 23% 35% 23%	2520
	21st to end	Day	10% 2 2 13% 32% 41%	2520
July	1st to 10th	Day	6% 1 2 9% 26% 56%	2451
	11th to 20th	Day	8% 2 3 10% 27% 49%	2445
	21st to end	Day	9% 2 3 9% 28% 50%	2449
August	1st to 10th	Day	9% 2 3 11% 27% 47%	2295
	11th to 20th	Day	6% 2 2 9% 34% 47%	2122
	21st to end	Day	7% 1 1 11% 36% 44%	2376
September	1st to 10th	Day	6% 1 3 8% 32% 50%	2160
	11th to 20th	Day	12% 2 5% 21% 38% 22%	2152
	21st to end	Day	12% 2 4 19% 37% 26%	1976
October	1st to 10th	Day	18% 3 7% 18% 26% 29%	1800
	11th to 20th	Day	17% 3 6% 20% 27% 27%	1800
	21st to end	Day	19% 3 6% 21% 28% 23%	1980
November	1st to 10th	Day	32% 3 8% 20% 21% 16%	1680
	11th to 20th	Day	28% 5% 8% 19% 27% 13%	1710
	21st to end	Day	30% 4 7% 19% 27% 13%	1653
December	1st to 10th	Day	35% 4 9% 19% 21% 12%	1520
	11th to 20th	Day	54% 4 5% 14% 14% 9%	1928
	21st to end	Day	39% 8% 14% 21% 12% 6%	2794
January	1st to 10th	Night	39% 5% 12% 24% 16% 4	4406
	11th to 20th	Night	48% 6% 9% 15% 12% 9%	4228
	21st to end	Night	49% 7% 9% 16% 12% 7%	4521
February	1st to 10th	Night	39% 3 6% 18% 20% 13%	2470
	11th to 20th	Night	36% 4 8% 23% 20% 9%	2228
	21st to end	Night	38% 3 8% 24% 20% 7%	1829
March	1st to 10th	Night	46% 5% 10% 17% 17% 5%	2147
	11th to 20th	Night	41% 5% 8% 19% 19% 7%	1980
	21st to end	Night	39% 6% 12% 22% 14% 6%	2063
April	1st to 10th	Night	35% 5% 15% 20% 19% 6%	1800
	11th to 20th	Night	31% 5% 12% 26% 17% 9%	1779
	21st to end	Night	24% 5% 11% 35% 18% 6%	1800
May	1st to 10th	Night	22% 5% 12% 25% 27% 8%	1757
	11th to 20th	Night	18% 3 12% 30% 26% 10%	1452
	21st to end	Night	20% 5% 13% 32% 24% 6%	1552
June	1st to 10th	Night	17% 5% 13% 23% 29% 13%	1440
	11th to 20th	Night	7% 3 7% 25% 33% 25%	1440
	21st to end	Night	9% 1 3 14% 34% 40%	1440
July	1st to 10th	Night	5% 1 2 10% 27% 56%	1400
	11th to 20th	Night	9% 2 4 12% 22% 52%	1392
	21st to end	Night	13% 2 2 8% 24% 51%	1625
August	1st to 10th	Night	12% 2 2 12% 26% 46%	1617
	11th to 20th	Night	8% 3 2 11% 30% 46%	1780
	21st to end	Night	7% 1 1 10% 32% 49%	1980
September	1st to 10th	Night	5% 2 2 7% 33% 50%	1800
	11th to 20th	Night	11% 2 3 19% 39% 26%	1806
	21st to end	Night	11% 2 2 21% 36% 27%	1980
October	1st to 10th	Night	18% 3 5% 18% 29% 27%	2160
	11th to 20th	Night	16% 3 6% 17% 31% 28%	2160
	21st to end	Night	15% 3 5% 21% 30% 25%	2376
November	1st to 10th	Night	27% 4 8% 20% 21% 19%	2397
	11th to 20th	Night	26% 4 7% 22% 27% 14%	2470
	21st to end	Night	30% 4 6% 19% 25% 15%	2524
December	1st to 10th	Night	36% 3 8% 20% 18% 15%	2660
	11th to 20th	Night	50% 4 6% 14% 18% 7%	3276
	21st to end	Night	45% 8% 11% 17% 12% 7%	4862

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	33% 11% 23% 20% 9% 3	180
	11th to 20th	Day	23% 6% 24% 32% 11% 3	298
	21st to end	Day	22% 9% 27% 24% 15% 3	407
February	1st to 10th	Day	28% 12% 23% 23% 11% 3	370
	11th to 20th	Day	22% 15% 31% 22% 8% 1	450
	21st to end	Day	24% 15% 30% 22% 8% 1	363
March	1st to 10th	Day	28% 21% 25% 19% 5% 1	420
	11th to 20th	Day	29% 18% 24% 18% 10% 2	420
	21st to end	Day	23% 19% 32% 20% 6%	462
April	1st to 10th	Day	21% 16% 35% 20% 7% 1	420
	11th to 20th	Day	19% 24% 28% 23% 6% 1	412
	21st to end	Day	11% 19% 31% 25% 12% 3	420
May	1st to 10th	Day	12% 20% 32% 25% 9% 3	423
	11th to 20th	Day	15% 17% 30% 23% 12% 4	448
	21st to end	Day	13% 15% 24% 31% 13% 5%	485
June	1st to 10th	Day	8% 13% 31% 30% 10% 8%	450
	11th to 20th	Day	5% 16% 34% 31% 10% 5%	450
	21st to end	Day	4 7% 37% 33% 11% 8%	450
July	1st to 10th	Day	1 5% 40% 35% 12% 8%	446
	11th to 20th	Day	2 2 33% 42% 12% 8%	444
	21st to end	Day	2 2 34% 40% 14% 8%	487
August	1st to 10th	Day	3 6% 37% 36% 13% 5%	447
	11th to 20th	Day	1 5% 38% 37% 14% 6%	437
	21st to end	Day	1 5% 35% 40% 15% 4	495
September	1st to 10th	Day	3 5% 40% 36% 14% 2	450
	11th to 20th	Day	4 12% 33% 36% 13% 2	450
	21st to end	Day	4 10% 33% 40% 11% 2	450
October	1st to 10th	Day	5% 12% 32% 34% 14% 3	450
	11th to 20th	Day	7% 11% 27% 34% 17% 4	450
	21st to end	Day	11% 11% 26% 32% 17% 4	495
November	1st to 10th	Day	16% 9% 21% 27% 20% 7%	276
	11th to 20th	Day	12% 8% 19% 34% 19% 8%	270
	21st to end	Day	16% 9% 19% 31% 20% 5%	243
December	1st to 10th	Day	20% 7% 24% 24% 17% 8%	180
	11th to 20th	Day	19% 9% 28% 26% 11% 6%	180
	21st to end	Day	25% 13% 22% 21% 13% 6%	198
January	1st to 10th	Night	23% 5% 21% 26% 18% 7%	760
	11th to 20th	Night	18% 5% 19% 38% 15% 4	760
	21st to end	Night	22% 5% 20% 29% 19% 5%	836
February	1st to 10th	Night	21% 5% 20% 33% 18% 3	760
	11th to 20th	Night	20% 7% 19% 31% 18% 5%	744
	21st to end	Night	22% 8% 19% 35% 14% 3	610
March	1st to 10th	Night	26% 7% 17% 32% 15% 3	720
	11th to 20th	Night	22% 7% 16% 29% 21% 5%	720
	21st to end	Night	23% 8% 19% 29% 19% 2	792
April	1st to 10th	Night	18% 3 17% 41% 19% 3	720
	11th to 20th	Night	16% 7% 19% 36% 19% 4	711
	21st to end	Night	11% 3 18% 38% 23% 5%	720
May	1st to 10th	Night	10% 5% 18% 40% 23% 4	677
	11th to 20th	Night	8% 4 12% 39% 34% 3	390
	21st to end	Night	8% 2 13% 36% 36% 5%	389
June	1st to 10th	Night	6% 3 11% 35% 40% 6%	360
	11th to 20th	Night	1 1 12% 44% 37% 5%	360
	21st to end	Night	2 9% 42% 42% 5%	360
July	1st to 10th	Night	1 2 43% 48% 6%	350
	11th to 20th	Night	2 5% 38% 48% 7%	348
	21st to end	Night	3 1 5% 30% 47% 14%	539
August	1st to 10th	Night	3 1 5% 40% 43% 9%	552
	11th to 20th	Night	1 8% 45% 38% 9%	712
	21st to end	Night	1 5% 41% 48% 5%	792
September	1st to 10th	Night	2 6% 45% 40% 7%	720
	11th to 20th	Night	4 1 10% 36% 39% 10%	720
	21st to end	Night	4 2 14% 39% 32% 9%	720
October	1st to 10th	Night	6% 3 14% 42% 27% 8%	720
	11th to 20th	Night	8% 3 12% 41% 31% 6%	720
	21st to end	Night	7% 4 16% 35% 25% 13%	792
November	1st to 10th	Night	14% 3 13% 36% 26% 8%	740
	11th to 20th	Night	12% 4 19% 38% 21% 6%	760
	21st to end	Night	15% 5% 21% 34% 19% 6%	760
December	1st to 10th	Night	22% 4 19% 34% 16% 5%	760
	11th to 20th	Night	27% 3 18% 31% 17% 4	760
	21st to end	Night	25% 7% 21% 29% 15% 3	836

Page generated at 2024-02-22 03:05:41. Version ac07

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